Compressor



Feb. 18, 1941. GUSTAFSQN 2,231,904

COMPRESSOR Original Filed Feb. 20', 1936 2 Sheets-Sheet l Kiwi:

Feb.'-18, 1941; A. N. GUSTAFSON coMPREssofi 2, Sheets-Shet 2 OriginalFiled Feb. 20, 1936 mmm? Gas/a 1%eyans.

Patented ob. 1 8,- 1941 PATENT OFFICE I 2.231.904 P corrrnssson AlfredN. Gustafson, West Chester, Pa, assignor to Schramm, Inc WestChester-J1, a corporation of Pennsylvania Original application February20, 1936, Serial No.

64,808. Divided and this application Septemher 1, 1938, Serial No.227,915

4 Claims. (Cl. 230-22) This invention relates to a compressor and I moreparticularly to a valve'arrangement which is particularly efiective inincreasing the. efficiency of a compressor and reducing its size for agiven capacity.

This application is a division of my application Serial No. 64,898,filed February 20, 1936',

While certain aspects of the present invention are of generalapplicability to compressors of a reciprocating piston type. theinvention is particularly directed to the type of compressor which maybe regarded as constructed by a conversion of an internal combustionengine. The-transfor- "mation of internal combustion engines intocompressors constitutes a very economical method of producing high speedcompressors. The engines are quite inexpensive because of quantityproduction and their running parts are so made as to be capable ofoperation at very high speeds. When'large size compressors are producedby such-transformation, all the cylinders of a multicylinder engine maybe turned into-compressor cylinders. On the other hand, where smallcompressor units are to be provided only some of the cylinders may betransformed, the remaining ones being left to function as enginecylinders so that a combination engine and compressor is provided. A-satisfactory arrangement of this latter sort is illustrated in 'SchrammPatent No.-

1,738,12l, dated December 3, 1929. As shown in this patent, the two endcylinders of a fourcylinder engine have been transformed into compressorcylinders, while the two intermediate cylinders continue to function asengine cylinders. In cases where all of the cylinders are transformed,there is, of course, used a separate motor or-engine for drivingpurposes.

In accordance with the practice heretofore used, there has beensubstituted a modified cylinder head in order that'a greater compressionratio may be attained in the compression cylinders than would bepermissible in engine cylinders, this substitution of head being alsoaccomplished by elimination of the mechanically operated engine valvesassociated with the compressor cylinders and substitution of manifolds,etc., to produce the proper and necessary passages.. Automatic valvesresponsive to air pressure have been provided in the substitute cylinderheads, all as shown in the Schramm patent referred to above.

One of the requirements, in addition to the transformations indicatedabove, is the provision of suitable unloading mechanism which will stopthe compressor action when the pressure in the inders by means such asillustrated in my. prior Patent N0. 2,023,418, dated December 10, 1 935,

so that as the compressor piston continues to reciprocate air isalternately drawn into and forced outwardl through the permanently heldvalve. Unloading of this nature is quite simply accomplished where thevalves are of automatic' vne- Automatic intake valves, however, are notparticularly satisfactory, inasmuchas, since they depend .for theiroperation upon air pressure, their operation variesquite considerably,depending upon the pressure in the receiver. Consider, for example, thediiferent conditions which exist when the receiver contains air at a lowpressure and when it contains air at high pressure.- There is alwaysresidual clearance in the cylinder when the piston is. at its inner deadcenter. The pressure above the piston at thistime depends upon thepressure of the receiver and is substantially equal to it. As the pistonthen recedes from its inner dead center position, an automatic intakevalve will not open until expansion of the gas in the cylinder, hastaken place to such extent that the pressure is below atmospheric by-anamount such that the difference' in pressure will serve to open theintake valve against the relatively weak spring which acts upon it tonormally hold it closed. It is obvious that the distance the piston mustmove before such opening takes place is very much affected by thepressure in the upper end of the cylinder when the piston is in its deadcenter position, which pressure is substantially equal to that of thereceiver. The action of the intake valve accordingly varies veryconsiderably with the receiver pressure and design can only be made tosheet proper working under one particular. condition. Desirably theintake valve should be open throughout substantially the entire intakestroke-of the piston.

The use of a mechanically operated intake valve will, of course, insurethat the intake valve will operate the same for all pressure conditions.Difficulties in unloading then arise. Proposals have been made toproduce unloading by throttling the intake of air. This procedure,however, is objectionable because the vacuum drawn above the Pistoncauses oil to pass into the upper portion. of the cylinder where, assuccessive compression and expansion of the residual, gas takes place,vaporization of the oil and consequent explosions may occur. There isalso the grave danger of having so much oil accumulate that, because ofthe close clearances involved, the piston may eventually break thecylinder head.

It is the broad object of the present invention to provide a compressorcombining the advantages of mechanically operated intake valves andautomatic exhaust valves which, it may be remarked, have the greatadvantage of acting as automatic safety valves. In utilizing this .com-

bination, the automatic exhaust valves can be considerably enlarged soas to take up most, if not all, of the end of thecylinders. The'emciencyis thereby increased, since a very small move- 8 ment of the exhaustvalve is necessary to provide a sufiiciently large passage for the freeflow of the compressed air to the receiver.

It is a further object of the invention to, provide improved unloadingarrangements suit- 10 able for use in connection with mechanicallyoperated intake valves.

The general'objects mentioned above, together with subsidiary objectsrelating particularly to details of construction, will be apparent fromthe 1 following description read in coniunction with the accompanyingdrawings, in which:

Figure 1 is an'enlarged transversesection of a compressor of L-head typeembodying the features of the invention; and 2 Figure 2 is a diagramshowing the associations of various elements with the compressor ofFigure 1, a conventional unloader valve being shown therein in enlargedlongitudinal section.

- Referring first to Figure 2, there is indicated 25 therein afour-cylinder engine the two end cylinders of which have been convertedinto compressor cylinders .by arrangement of parts as shown in Figure 1,intermediate cylinders being adapted to act as engine cylinders tofurnish 30 the drive. It will be obviouswthat the invention is alsoapplicable to cases in which there is an individual compressor and motoror separate engine. The substituted cylinder head in the caseillustrated may, as usual, be so arranged as 85 to maintain conventionalconditions at the ends of the cylinders; at the same time, however,providing close clearances in the compressor cylinders to secure maximumpressures and emciency of operation. In the present case. a sub- 40stitute intake manifold 8 is illustrated communicating only with theintake passages of the engine cylinders, the manifold being connected toa conventional carburetor 8. The intake passages I0 of the .compressorcylinders may be 45 opened directly to the atmosphere or, if desired,may be connected to suitable air filters to avoid accumulation of dirtin the compressor mechanism. The exhaust manifold I2 may still be used.The exhaust valves of the compressor cyl- 50 inders are renderedinoperative by removing; for

example, the intermediate follower elements located between them andtheir operating cams. Preferably, however, particularly where there is acomplete transformation to a compressor, a

85 substitute cylinder block is provided to eliminate the exhaustpassages entirely.

Referring now to Figure 1, there is shown therein the unloadingarrangement for the compressor. In this case the intake valve 82 is con-60 tinuously operated through the pusher 80 by the cam 80,,on the camshaft. The passage 00 from the automatic discharge valve 24 normallycom-.

. municates through 88 with the receiver 88. A valve 82 is arranged toalternatively seat on an 65 upperseat carried by .the lower end ofa'fittlng' 84 or upon a lower seat 81,- in which latter position it willcut of! communication between 00 and 88. A passage I00 furnishescommunication between the atmosphere and the upper side 'of 70the valve02.

into its upper seated position by a spring I02 iiffiarriesz at the upperend Oflts spindle, a piston I04 slidingin a cylinder I08 and arranged tobe forced downwardly by air entering a tube 7 I08 arranged to receiveairat recelverpressure.

The valve 82 is normally urged "I'he piston I04 is sufflciently largethat upon communication of the upper end of the cylinder I08 with thereceiver the'valve 02 will be snapped, downwardly against itslo'wer seat81 with the result that communication is established between 5 thedelivery side ofthe automatic delivery valve and the atmosphere. As thecompressor continues to operate after this unloading takes place,

the piston I8- will draw air inwardly past the continuously operatedintake valve 82 and will 10 force it outwardly throughthe delivery valve24 to the atmosphere. Since the springs holding the delivery valveclosed are very light, noappreciable amount of work is done in thisaction. At the same time there is no danger that oil will get above thepiston. I

' Connection between the tank 30 and the tubes I08 occurs through a line54 in which there is interposed a suitable snap valve of conventionaltype illustrated in detail in Figure 2. 2

The snap valve is of the type illustrated in -my prior Patent No.2,023,418, dated December 10, 1935. This valve comprises a casing 82surmounted by a bonnet 84 connected to the tank 80. A disc 88 havingplane faces is located with- 25 in an upper cylindrical portion of thebore of casing 82 and is adapted for vertical movement between anannular plane seat 88 formed on bonnet 84 and an annular plane seat I4formed on the upper end of a bushing 12. iThe disc and seats areflnelyground to insure air-tight contact between the disc faces and therespective seats. The disc flts the bore of the casing loosely whereby aslight clearance "is provided between its edge and the wall of the borefor leakage of air. 85

A spring I8 extending through-bushing 12 normally forces the discagainst seat 88, its tension being adJustable by inward or outwardmovement of its abutment provided on a screw I8 threaded into theinterior of the casing. A hole 80 ex- 40 tending axially through thescrew furnishes communication between the interior of the casing belowthe disc and the atmosphere. A screen 8| prevents dirt particles fromthe tank 48 from entering the valve and causing faulty seating ofthedisc. v

A fitting 82 communicates with the interior of the casing outside. ofand below seat I4. The fitting is connected to the air line I08 whichcommunicates with the various spaces above the V pistons I04. Withinthis fitting is a ball check valve resting on a seat '08 and retained inthe fitting by cross pin 88.

In the operation of the device, so long as the pressure in-the supplytank is below the prede- 55 tel-mined maximum, the disc 88 will be heldagainst its upper seat, and consequently the spaces above the pistonsI04 will be open to the atmosphere through the ball check 84, which hasa faulty fit upon its seat 00 so as to permit a slow 80 leakage of air.Under such conditions the spring I02 maintains the valve 82 in its upperposition so that the cylinders may supply compressed air to the tank 20through the exhaust valves 24. When the pressure in the tank 80 reachesa predetermined amount, the disc 88 is snapped to its lower seat onwhich it is held by reason of the effective increase of area acted uponby the-air at tank pressure. Air at the pressure of the tank then flowspast the check valve 84 and depresses the pistons I04, moving the valves82 to their lower seats so that air may be forced past the valves 24directly to the atmosphere.

- When the pressure in the tank falls to a predetermined minimum, thedisc 88 would be and held there by reason 01" the fact that the area onthe upper side of the discis now substantially reduced. When thisoccurs, the spaces above the pistons I04 are open to the atmosphere andthe compressed air may flow therefrom, preferably slowly, past the illfitting check 84. This check is desirable inasmuchas the slow upwardmovement of the pistons Ill would insure that the engine shaft will makean appreciable number ofrevolutions before the load ls taken by theengine. In general an engine compressor unit of this character isfurnished with a governor which is somewhat sluggish in operation andshould be permitted to open the engine throttle before full load isimposed on the compressor. The delay provided by the slow movement ofthe valve 92 during compression strokes of the compressor pistonsenables the governor to furnish sufiicient mixture to the engine as theload is gradually increased to avoid any sudden shock. of course, if theshock is immaterial, the check 84 may be eliminated, whereupon as soonas the valve 68 operatesdelivery of compressed air to the tank will takeplace.

It will be obvious that with the above arrangement the'pressure in thecylinder remains constantly approximately atmospheric during an unloadedperiod, the deviations from atmospheric pressure being only the minorones due to friction in the passages and the light pressure of theexhaust valve springs.

It will be clear that numerous changes in the embodiment of theinvention may be made without departing from its scope.

What I claim and desire to protect by Letters Patent is:

1. In combination, a receiver for compressed gas, a compressor connectedto said receiver to deliver gas thereto including a cylinder andreciprocating piston therein, an intake valve for the cylinder, meansfor mechanically actuating the intake valve, and an exhaust valveoperated automatically by the gas compressed in the cylinder when itspressure exceeds that in the receiver, and means for unloading thecompressor when the pressure in the receiver exceeds a predeterminedamount, said last named means comprising a valve arrangement to engagealternatively either of two seats and adapted when engaging one seat toprovide for passage of gas from the exhaust valve to the receiver andwhen engaging the other seat to open the discharge side of the exhaustvalve to the atmosphere and cut off communication between the exhaustvalve and the receiver so that the pressures in the cylinder remainapproximately atmospheric during unloading periods, and means foreiIecting complete movements of said valve arrangement between said twoseats when such movements begin.

. 2. In combination, a receiver for compressed gas, a compressorconnected to said receiver to deliver gas thereto including a cylinderand reciprocating piston therein, an intake valve for the cylinder,means for mechanically actuating the intakevalve,and an exhaust valveoperated automatically by the gas compressed in the cylinder when itspressureexceeds that in the receiver, and means for unloading thecompressor engaging one seat to provide for passage of gas from theexhaust valve to'the receiver and when engaging the other seat to openthe discharge side of the exhaust valve to the atmosphereand.

cut oil communication between the exhaust valve and the receiver so thatthe pressures in the cylinder remain approximately atmospheric duringunloading periods, means for effecting complete movements of said valvearrangement between said two seats when such movements begin, and meansfor slowing down movement of the valve arrangement to position toprovide passages of gasfrom the exhaust valve to the receiver so thatload is applied gradually to the compressor.

3. In combination, a receiver for compressed gas, a compressor connectedto said receiver to deliver gas thereto including a cylinder andreciprocating piston therein, an intake valve for the cylinder, meansfor mechanically actuating the intake valve, and an exhaust valveoperated automatically by the gas compressed in the cylinder when itspressure exceeds that in the receiver, and means for unloading thecompressorwhen the pressure in the receiver exceeds a pre determinedamount, said last named means comprising a valve arrangement to engagealternatively either of two'seats, the space within which the valvearrangement moves between the seats being continuously in communicationwith the discharge side of the exhaust valve, the side of one of theseats opposite the valve arrangement being continuously in communicationwith the atmosphere, and the side of the other of the seats opposite thevalve arrangement being continuously in communication with the receiver,and means responsive to the receiver pressure for eflecting movements ofthevalve arrangement from one seat to the other and pre venting floatingof the valve arrangement'between the seats.

4. In combination, a receiver for compressed gas, a compressor connectedto said receiver to deliver gas thereto including acylin-der and re--ciprocating piston therein, an intake valve for the cylinder, means formechanically actuating the intake valve, and an exhaust'valve operatedautomatically by the gas compressed in the cylinder when its pressureexceeds that in the receiver, and means for unloading the compressorwhen the pressure in the receiver exceeds a pre-- determined amount,said last named means comprising a valve arrangement to engagealternatively either of two seats, the space within which the valvearrangement moves between the seats being continuously in communicationwith the discharge side of the exhaust valve, the side of one of theseats opposite the valve arrangement being continuously in communicationwith the atmosphere, and the side of the ,other of the the valvearrangement to position to provide passage of gas from the exhaust valveto the receiver so. that load is applied gradually to the 'compressor.

' ALFRED N. GUS'IfAFSON.

